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Rise of the replicators

Video: See the first machine designed to reproduce itself

By Tom Simonite

I AM standing in a cold north London workshop looking expectantly at a bizarre metal and plastic contraption. An acrid smell drifts from the machine as a length of plastic is drawn into a barrel at its centre and heated up. The molten plastic squirts from a nozzle onto a platform moving beneath it, drawing a pattern. The nozzle also moves up and down to build the design upwards like an expert cake icer.

Over the next few minutes, this “MakerBot” will do something I can only dream of doing&colon; it will create a spare part of itself as an insurance against future mishaps. Staring at the Heath Robinson-style kit before me, it is hard to believe that it – and a few hundred other devices – are paving the way to an era of desktop machines that can make just about anything, including copies of themselves.

It could be a revolutionary age. MakerBot is one of a range of desktop manufacturing plants being developed by researchers and hobbyists around the world. Their goal is to create a machine that is able to fix itself and, ultimately, to replicate.

To find out how close we are to that goal, I have come to the London Hackspace, a communal workshop where Russ Garrett, a software developer by day, keeps his MakerBot. Like 900 other enthusiasts, Garrett bought a mail-order kit from MakerBot Industries of New York for &dollar;750, and built the machine himself.

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MakerBot and most of its kin are essentially a cut-price reinvention of the 3D printer. While professional machines still cost upwards of tens of thousands of dollars, a coalition of academics and tinkerers has created versions that do much the same thing for much less. Anyone with a few hundred dollars and some spare time can build their own 3D printer from a set of plans distributed free on the internet.

“Anyone with a few hundred dollars and some spare time can build a 3D printer from a set of free plans”

These machines can build any number of things, including everything from coat hooks to ipod docking stations. One MakerBot owner even made his engagement ring with it. But key to MakerBot’s popularity is its ability to make its own spares. Every kit contains a handful of parts made by other MakerBots, linking them in a mechanical family tree.

The MakerBot lineage is descended from RepRap (see “The replicant”) – the first machine designed to replicate parts of itself and brainchild of Adrian Bowyer, a mechanical engineer at the University of Bath, UK. In 2006 he started the project with two goals&colon; to create a 3D printer that anyone could make and use, and to make it capable of self-replicating. Most importantly, it would have an open-source design to encourage anyone to modify and improve it.

At the moment, RepRap can build about half of its own parts, including joints and casings. Some components, such as steel rods and microprocessors, are beyond its capabilities as yet. Still, Bowyer’s mechanical progeny reached a major milestone in November 2008, when Canadian Wade Bortz announced he had used his RepRap to create all the parts of a replica that it was possible to print – the first time this had been done “in the wild” outside Bowyer’s lab. It was sold online a few months later for a case of beer.

Bowyer’s first design, called Darwin, has since been replaced by Mendel, which is smaller and more reliable. “Mendel can, if you discount nuts and bolts, print 50 per cent of the machine’s parts in under three days,” says Bowyer. Mendel can make about the same proportion of its own parts as Darwin, but Mendel is a simpler, smaller and more reliable machine. It can also make much larger things than Darwin can.

Since then, tens of others have made mothers out of their machines, sometimes selling their offspring for hundreds of dollars to other enthusiasts keen to get a machine of their own. This has led to a veritable ecosystem of RepRap-type machines – an estimated 3000 exist – and while Bowyer is now focused mainly on making Mendel more robust and user-friendly, the RepRaps in the wild have begun evolving into different forms.

While exploring the RepRap forums, I come across one with the potential to be more self-replicating than any before, and it is provoking some excited comments. The poster, Frank Davies, based in Houston, Texas, is the proud owner of a RepRap ingeniously built using parts salvaged from a dot matrix printer and a Xerox photocopying machine, and he is now working on making his RepRap totally printable.

NASA engineer’s double life

Davies, by day a NASA engineer on the space shuttle programme, is effectively replacing RepRap’s skeleton with one of his own making. In place of the tracks along which the print nozzle glides are plastic concertina-like mechanisms called Sarrus linkages, originally used to ensure steam pistons moved in straight lines in an era when reliably straight rods weren’t available. Two perpendicular hinges connect the moving parts such that they can move only along the remaining, unrestricted axis.

“Another member of the community mentioned this linkage, so I Googled it and ran with the idea,” says Davies. The result is a prototype whose platform moves in two directions without using a single steel rod. Davies is working on adding the third axis and print head to make a species of RepRap able to print an unprecedented amount of itself. “If it goes well, it should be done in a few months,” he says. “Since I’ve got a printer that can make arbitrarily shaped objects, it’s not hard to try new things out.”

Other attempts to make more parts printable include replacing the machine’s rubber belts with printed rack-and-pinion gears. But there is a limit to how much of a machine can be made with plastic alone. What we need is a machine that can create parts made from a number of different materials.

The search leads me to Neil Gershenfeld, head of the Center for Bits and Atoms at the Massachusetts Institute of Technology. Gershenfeld is busy promoting FabLabs&colon; rooms the size of a squash court packed with all the equipment necessary to take any design and make working products at a quality to match that of a professionally commissioned prototype. He has been spreading the word – so far there are FabLabs in Afghanistan, the Netherlands, Costa Rica, Ghana, the UK, Kenya, and the South Bronx in New York. In the process he has realised that what FabLabs really need is to be able to make themselves. “The tools will have really succeeded when they can do that,” he says.

In a year or two, FabLabs will simply be made inside existing ones, Gershenfeld promises. “We’ll still buy some components, like microcontrollers and stepper motors, but we’ll make everything else.”

A machine called MultiFab, created by recent MIT graduate Ilan Moyer, backs up that claim. Like RepRap, it is made from parts and materials costing just &dollar;400. It too can print plastic, but it can also wield milling and cutting toolheads to carve shapes in wax, cut vinyl, mill light plastic and wood, and carve out the conductive traces of custom circuit boards. The first thing the completed machine did was to carve out a circuit board to replace one of its own.

Moyer has experimented with using it to perform sequential operations – printing a structure, and then putting the finishing touches to its shape with a milling tool – and plans to add a laser cutting head. “Eventually I want to be able to put a FabLab in a briefcase,” he says.

Still, ingenious as these machines are, they merely churn out piles of parts. What about assembly? A heap of plastic and metal is not a machine, just as you don’t have much in common with a pile of flesh and bones.

Greg Chirikjian, a roboticist at Johns Hopkins University in Baltimore, Maryland, agrees. “When a prototype only makes parts, the machine that made those parts wasn’t reproduced,” he says. A true self-replicator must handle both fabrication and assembly. Chirikjian and his colleague Matt Moses are aiming to achieve this with a kind of Lego set that doesn’t need anyone to play with it.

The pair have already demonstrated key parts of such a system, using around 100 plastic blocks. Although it cannot yet fabricate these blocks itself, the machine is able to move in 3D to pick up and bind them into larger structures. Moses is currently working on having it make a complete replica of its own structure using Lego-like bricks, though the machine still relies on conventional motors – which have to be installed by hand – to drive its activity.

The blocks are simple rectangular plates with two threaded holes and four cone-shaped connectors, shot through with metal wiring so they can be used to create electronic circuits if need be. The machine uses a screwdriver-like tool to pick up, stack or secure blocks together. A line of basic blocks assembled together can act as a slide along which other components – made from groups of their siblings – can move driven by an attached motor.

The blocks are made from polyurethane, and the processes needed to make them could be mastered by a desktop machine, says Chirikjian. The machine could squirt a substance such as silicone over a spare part of itself to make a mould, before pumping in polyurethane to reproduce the original. The pair have shown that gaps left for wiring can be filled by a RepRap head modified to deposit a low-melting-point alloy. With the addition of a few magnets, Moses has now made a functional, if weak, motor.

This looks really promising&colon; desktop machines capable of making complex electrical components should in theory be able to create copies of their own electronic brains. Hod Lipson, a robotics researcher at Cornell University in Ithaca, New York, says much more is possible. His students run a RepRap-like 3D printer project called Fab@Home, whose design boasts two syringes allowing it to squirt out two materials at a time. Researchers in Lipson’s lab are using a similar multi-barrelled approach to collapse printing and assembly into a single step, by printing fully functional modules that do not need to be assembled.

“We’re at the transition from printing parts to printing systems,” says Lipson, “and working hard on printing a complete robot.” The team will know when that milestone has been reached, he says, on the day the thing they print walks, or more likely crawls, from the printer under its own power.

So far the team has managed to print out working versions of the major components of a robot&colon; electronic muscle actuators, relays, transistors, batteries and circuitry. Electrodes and wiring, for example, can be made using silver particles mixed into silicone, while the bulk of a battery can be made using a paste of zinc particles and liquid electrolyte. A robotic arm stands by to swap syringe cartridges as required.

Although the components are far inferior to off-the-shelf parts, Lipson is confident that his team need only find the right materials. His goal is to find a relatively small palette that can be mixed to create a wide range of components. “Just as red, green and blue can be used to print full colour, this will be very powerful.”

“The goal is to find a small palette of materials that can be mixed to create a much wider range”

Lipson’s team still has a mountain to climb before it can print the sort of microchips that control his machines, and besides that, replicating machines have a fundamental limitation, he says&colon; “The thing you print can’t be as accurate as the thing you printed it with.” Though the machines’ offspring may be perfectly functional for several generations, tiny errors will gradually accumulate so parts will periodically need to be replaced. And they will never be as precise as the originals.

This by no means sounds the death knell for self-replicating machines, says Bowyer. Every living thing can be seen as a self-replicating machine that relies heavily on components and assistance from others, he says, so why should machines be any different? Plants, mosquitoes and viruses are all accepted as self-replicating but rely heavily on other species to achieve it. It would be churlish to expect replicators to be any different.